Electrophotographic printing is a well-known and commonly used method of copying or printing documents. Electrophotographic printing is performed by exposing a light image representation of a desired document onto a substantially uniformly charged photoreceptor. In response to that light image the photoreceptor discharges, creating an electrostatic latent image of the desired document on the photoreceptor's surface. Toner is then deposited onto that latent image, forming a toner image. The toner image is then transferred from the photoreceptor onto a receiving substrate such as a sheet of paper. The transferred toner image is then fused with the substrate, usually using heat and/or pressure. The surface of the photoreceptor is then cleaned of residual developing material and recharged in preparation for the production of another image.
The foregoing generally describes black and white electrophotographic printing machines. Electrophotographic printing can also produce color images by repeating the above process for each color of toner that is used to make the color image. For example, the photoreceptive surface may be exposed to a light image that represents a first color, say black. The resultant electrostatic latent image can then be developed with black toner particles to produce a black toner layer that is subsequently transferred onto a receiving substrate. The process can then be repeated for a second color, say yellow, then for a third color, say magenta, and finally for a fourth color, say cyan. When the toner layers are placed in superimposed registration the desired composite color toner image is formed and fused on the receiving substrate.
The color printing process described above superimposes the color toner layers directly onto a substrate. Other electrophotographic printing systems use intermediate transfer belts. In such systems successive toner layers are electrostatically transferred in superimposed registration from the photoreceptor onto an intermediate transfer belt. Only after the composite toner image is formed on the intermediate transfer belt is that image transferred and fused onto the substrate. Indeed, some electrophotographic printing systems use multiple intermediate transfer belts, transferring toner to and from the belts as required to fulfill the requirements of the machine's overall architecture.
In operation, an intermediate transfer belt is brought into contact with a toner image-bearing member such as a photoreceptor belt. In the contact zone an electrostatic field generating device such as a corotron, a bias transfer roller, a bias blade, or the like creates electrostatic fields that transfer toner onto the intermediate transfer belt. Subsequently, the intermediate transfer belt is brought into contact with a receiver. A similar electrostatic field generating devices then transfers toner from the intermediate transfer belt to the receiver. Depending on the system, a receiver can be another intermediate transfer member or a substrate onto which the toner will eventually be fixed. In either case the control of the electrostatic fields in and near the transfer zone is a significant factor in toner transfer.
Intermediate transfer belts often take the form of seamed belts fabricated by fastening two ends of a web material together, such as by welding, sewing, wiring, stapling, or gluing. While seamless intermediate transfer belts are possible, they require manufacturing processes that make them much more expensive than similar seamed intermediate transfer belts. This is particularly true when the intermediate transfer belt is long. While seamed intermediate transfer belts are relatively low in cost, the seam introduces a discontinuity that interferes with the electrical, thermal, and mechanical properties of the belt. While it is possible to synchronize a printer's operation with the motion of the intermediate transfer belt such that toner is not electrostatically transferred onto the seam, such synchronization adds to the printer's expense and complexity, resulting in loss of productivity. Additionally, since high speed electrophotographic printers typically produce images on paper sheets that are cut from a paper “web,” if the seam is avoided the resulting unused portion of the paper web must be cut-out, producing waste. Furthermore, even with synchronization the mechanical problems related to the discontinuity, such as excessive cleaner wear and mechanical vibrations, still exist.
Acceptable intermediate transfer belts require sufficient seam strength to achieve a desired operating life. While the desired operating life depends on the specific application, typically it will be at least 100,000 operating cycles, and more preferably 1,000,000 cycles. Considering that a seamed intermediate transfer belt suffers mechanical stresses from belt tension, traveling over rollers, moving through transfer nips, and passing through cleaning systems, achieving such a long operating life is not trivial. Thus the conflicting constraints of long life and limited topographical size at the seam places a premium on adhesive strength and good seam construction.
A prior art “puzzle cut” approach to seamed intermediate transfer belts significantly reduces mechanical problems by producing an improved mechanical seam.
U.S. Pat. No. 5,514,436, issued May 7, 1996, entitled, “Puzzle Cut Seamed Belt;” U.S. Pat. No. 5,554,193, entitled “Endless Seamed Belt with Low Thickness Differential Between the Seam and the Rest of the Belt,” and U.S. Pat. No. 5,487,707, issued Jan. 30, 1996, entitled “Puzzle Cut Seamed Belt With Bonding Between Adjacent Surface By UV Cured Adhesive” teach the puzzle cut approach. While puzzle cuts reduce mechanical problems there remains other difficulties with transferring toner onto and off of a seam of a seamed intermediate transfer belt.
The process of cutting the petals in the belt material to form the puzzle cut joints presents a challenge to those attempting full automation. There is a continuous need through out the cutting process to maintain close tolerances. These tolerances require high precision in the handling of the belt material and the continuous registration of the belt material with the cutting and handling apparatus. In addition this must be accomplished while maintaining the belt material free of contamination.
It is a purpose of the system of this application to provide an automated system and process for cutting the belt material in preparation for joining the ends of the belt material into a continuous belt. It is another purpose of this system to accomplish this while minimizing contamination and damage. It is another purpose of the system of this application to maintain accurate positioning of the belt continuously through the cutting process.